Ceramic articles containing spaced longitudinal ducts in which the elongated ducts are parallel, possess high compressive strength longitudinally. These articles are useful as catalyst supports and heat exchange elements.
Honeycomb articles containing a plurality of spaced parallel ducts have been manufactured from plastics, using an apparatus which includes a support plate with channels and a large number of shaping elements screwed centrally onto the support plate. The shaping elements have the dimensions and conformation corresponding to the cross-section of the elongated ducts.
It is possible with such an apparatus to extrude plastic articles in the form of a continuous circle. It is not, however, possible to extrude relatively viscous compounds such as ceramic materials with such an apparatus, because the strength and stability of the apparatus is inadequate for the extrusion pressures required.
More particularly, it has been difficult or impossible to manufacture with such an apparatus ceramic articles containing ducts of an extremely small diameter. The problems involved in fastening the shaping elements on the support plate, and also the incorporation of the feed bores for the material in the support plate, have in the past led to the production of only relatively large hollow channels in a finished ceramic honeycomb element.
Various multi-element devices including a plurality of forming members have been proposed for use in extruding ceramic articles to alleviate the above-noted problems. In general, these multi-element devices require disassembly of the die into its multiplicity of elements for cleaning, and subsequent re-assembly for use. This disassembly and re-assembly for cleaning adds to the labor expense of a manufacturing operation using such a die structure. Further, the possibility exists that the material being extruded may sometimes cure or stiffen in the die to an extent that makes disassembly of the die difficult or impossible. In such multi-element dies, the die must be disassembled immediately after use and cleaned or there is a possibility of the die thereafter being usable only after an involved cleaning operation or becoming inoperative.